This application relates generally to a disc drive and more particularly to an actuator assembly of the disc drive.
One function of a disc drive is reliable storage and retrieval of information. Using one common implementation of a disc drive as an example, data is stored on one or more discs coated with a magnetizable medium. Data is written to the discs by an array of transducers, typically referred to as read/write transducers, mounted to an actuator assembly for movement of the transducers relative to the discs. The information is stored on a plurality of concentric circular tracks on the discs until such time that the data is read from the discs by the read/write transducers. Each of the concentric tracks is typically divided into a plurality of separately addressable data sectors. The transducers are used to transfer data between a desired track and an external environment. During a write operation, data is written onto the disc track and during a read operation the transducer senses the data previously written on the disc track and transfers the information to the external environment. Critical to both of these operations is the accurate locating of the transducer over the center of the desired track.
Conventionally, the transducers are positioned with respect to the disc surfaces by an actuator arm controlled through a voice coil motor. The voice coil motor is responsible for pivoting the actuator arm about a pivot shaft, thus moving the transducers across the disc surfaces. The actuator arm thus allows the transducers to move back and forth in an accurate fashion between an inner radius and an outer radius of the discs. The actuator arm is driven by a control signal fed to the voice coil motor at the rear end of the actuator arm. A servo control system is used to sense the position of the actuator arm and control the movement of the transducer above the disc using servo signals read from the servo segments on the disc surface in the disc drive. The servo control system relies on servo information stored on the disc. The signals from this information generally indicate the present position of the transducer with respect to the disc, i.e., the current track position. The servo control system uses the sensed information to maintain transducer position or determine how to optimally move the transducer to a new position centered above a desired track. The servo system then delivers a control signal to the voice coil motor to rotate the actuator arm to position the transducer over a desired new track or maintain the position over the desired current track.
As the demand for smaller disc drives increases, so does the demand for higher storage capacities. To meet this demand, manufacturers of disc drives are continually developing smaller yet higher storage capacity drives. Typically, to increase the storage capacity of a disc drive, the density of the concentric tracks on the disc is increased. In order to increase the track density, manufacturers either narrow the width of the concentric tracks or reduce the spacing between tracks.
Currently, most drives are limited to a track density around 50,000 tracks per inch. As the demand for a higher storage capacity continues to increase, so will the need for a track density higher than the conventional 50,000 tracks per inch. However, current drive track density is limited by various characteristics associated with the dynamic behavior of the actuator arm and voice coil motor assembly. A conventional actuator arm and voice coil motor assembly moves an attached read/write transducer over a large dynamic range. This large dynamic range hinders disc drive manufacturers from developing drives having a higher track density. As the track density increases, it becomes increasingly difficult for the servo system to accurately position the read/write transducer over the desired servo track.
One potential solution is to employ a microactuator for fine position control in addition to the conventional actuator, thereby effecting transducer positioning through dual-stage actuation. Various microactuator designs have been considered to accomplish high-resolution transducer positioning, including piezoelectric, electromagnetic, electrostatic, capacitive, fluidic, and thermal actuators. Additionally, various locations for the microactuator have been suggested, including on the slider and various other positions on the actuator arm. With regard to dual-stage actuation, the microactuator is a high-resolution actuator responsible for fine control of the read/write transducers attached to the microactuators and not accessing the entire surface of the disc. Accordingly, the actuator arm voice coil motor assembly is responsible for accessing tracks when seeking greater distances, i.e. low-resolution actuation.
Against this backdrop the present invention has been developed. The present invention is an intrinsically excitable actuator assembly allowing a transducer assembly a full range of access over a data storage medium. The intrinsically excitable actuator assembly includes an intrinsically excitable element that is excited in response to a control signal. The excitement of the intrinsically excitable element produces a movement of the element that is magnified by a motion amplification system. The magnification of the element movement results in positionally displacing a transducer assembly to access a desired location on the data storage medium. In accordance with a certain embodiment of the present invention, the intrinsically excitable element is piezoelectric material. The piezoelectric material is excited by a voltage, or electrical potential, applied to the material. Alternatively, the element may be constructed from a material with high magnetostrictive properties.
In accordance with still other embodiments, the present invention relates to a device for positioning a transducer assembly, in response to a signal from a controller, at any desired location relative to a data storage medium in order to write data to and read data from the medium. The device includes an elongated flexure supporting the transducer assembly and operable to position the transducer assembly over the desired location on the storage medium. The device also comprises an intrinsically excitable element contacting the flexure. The excitable element moves in response to an excitation produced by the signal from the controller and the flexure is configured to amplify the element movement to selectively position the transducer assembly over the desired location on the data storage medium.
In accordance with certain embodiments of the present invention, the data storage medium may be a recordable disc in a disc drive and the transducer assembly writes data to and reads data from a desired track of the recordable disc. The device may further include an actuator arm supporting the elongated flexure. The actuator arm is attached to a stationary support and has an interior surface constraining the intrinsically excitable element such that the movement produced by the excitation is concentrated to a point of contact between the intrinsically excitable element and the elongated flexure.
In accordance with still other embodiments, the present invention relates to a method for positioning a transducer assembly, in response to a signal from a controller, at any desired location relative to a data storage medium in order to access, or write data to and read data from, the medium. The method includes determining a control parameter associated with the signal to position a transducer assembly over a desired location on the medium. The control parameter is determined based upon a current location being accessed on the data storage medium. The method also includes exciting an intrinsically excitable element using the control parameter. The excitement produces a movement of the intrinsically excitable element. The method also includes amplifying the movement to selectively position a transducer assembly over the desired location on the data storage medium.
These and various other features, as well as advantages which characterize the present invention, will be apparent from a reading of the following detailed description and a review of the associated drawings.